Internal combustion engines may utilize a particulate filter in the exhaust to reduce the amount of emitted particulate matter. The particulate filter traps particulate matter, for example on a porous substrate through which the exhaust gasses flow. Once a particulate filter reaches its soot load capacity, back pressure to the engine may increase, decreasing fuel economy. Further, excess particulates may be released to the atmosphere, degrading emissions.
Under relatively high engine loads, exhaust temperature may be high enough to commence and sustain regeneration of the filter, during which soot accumulated on the filter burns and is thereby removed. Under relatively low engine loads, exhaust temperature may not be high enough to commence or sustain regeneration. In this case, various mechanisms may be used to increase exhaust heat and thus raise exhaust temperature sufficient for regeneration. However, the excess heat is frequently provided by mechanisms that utilize fuel without creating useful power for the engine, such as electric heaters or fuel injected to the exhaust, thereby decreasing fuel economy. As such, timing of the filter regeneration may be scheduled based on an expected route and engine load settings in order to regenerate the filter in a way that reduces wasted fuel.
Nevertheless, due to modeling errors and variation in operating conditions that affect the actual soot loading, it can be difficult to properly plan filter regeneration according to a planned engine load setting over a trip. In particular, small variations in actual soot loading over relatively long engine operation (such as cross country trips) quickly render such planning ineffective.
Engine systems may further include exhaust gas recirculation (EGR), where a portion of the engine exhaust is recirculated back to the intake manifold and inducted to the cylinders of the engine, in order to reduce combustion temperatures and lower NOx production. Some EGR systems include one or more EGR devices, such as coolers or mixers, to reduce the temperature of the exhaust to a desired temperature and/or effectively mix the EGR with intake air. Similar to the particulate filters described above, these EGR devices may also trap particulates and become ineffective if a soot load on the EGR device reaches a threshold. To regenerate an EGR device, exhaust temperature may be increased to burn the particulate matter, for example. Such EGR device regeneration suffers from the same issues described above for particulate filters, including wasted energy used to perform the regeneration and/or difficulty in planning an appropriate time for regeneration.